Photographic roll film transfer process



April 1959 H. c. YUTZY EI'AL PHOTOGRAPHIC ROLL FILM TRANSFER PROCESS Filed'Qct. 51, 1955 .13 OVERCOAT/NG L A YE R L AYE R m- SUPPORT RECEIVING LAYER SPOOL .l-' i g3 PHOTOSBVSIWVE SIDE llll g HenryO. Yaigz LeonardWTiwg I VENTORS 99M BY Q M ATTORNEYS United States Patent PHOTOGRAPHIC ROLL FILM TRANSFER PROCESS Henry C. Yutzy and Leonard W. Tregillus, Rochester,

N.Y.-,. assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Application October 31, 1955, Serial No. 543,886 8 Claims. (Cl. 96-29) This invention relates'to photography and particularly to a photographic transfer process for use in the reproduction of line or printed material 'or continuousv tone images.

This application is a continuation-in-part of application Serial No. 285,856, filed May 3, 1952, Patent No. 2,740,717.

Processes for the preparation of direct positive images by transfer procedures have been described in the literature. These methods involve in general the development of an exposed silver halide emulsion layer to metallic silver in the usual way, the transfer of the residual undeveloped silver halide from the unexposed areas by means of a silver halide solvent in the developer to a receiving sheet pressed in contact with the negative. The receiving sheet bears development centers upon which the dissolved silver halide or silver halide complex is deposited as metallic silver by physical development, using the chemical energy from the conventional photographic developing agents to effect this physical development. Various modifications have been described in which the steps were carried out separately or in combination, the prior art having been discussed in an article by Varden' in Journal of the Photographic Society of America, vol 13, September 1947, page 551.

In prior transfer processes the transfer has been made from a sensitive material on one support to a receiving layer on a second support, or between two layers on the same side of one support, one of which layers is later removed so that the image in either the remaining layer orthe -removed layer can be viewed.

Previously when the light-sensitive layer and receiving layer have been coated on a single support, it has been necessary either to expose the light-sensitive layer or view the transferred image through the support or to make the camera exposure through a prism in order to obtain a right-reading positive. A correctly oriented positive is also obtained when the light-sensitive layer and receiving layer are on separate supports.

It is an object of the present invention to provide a method for obtaining a right-reading direct positive image using only one support for exposure and formation of the positive. It is a further object of the present invention to provide a simplified transfer process for the production of direct positive images. It is also an object of this invention to provide a means and process for obtaining a positive image from a negative image on a single support without removing either the negative layer or the layer carrying the transferred image. Other objects will be apparent from the following description of our invention.

These objects are accomplished by providing a lightsensitive layer on one side of a visually opaque support andanimage-receiving layer on the opposite side of the support, exposing the light-sensitive layer to form an image therein and rolling the support on itself to allow the light-sensitive layer to come in contact with the image 2,882,151" Patented Apr. 14, 1959 ice receiving layer and transfer an image-forming compound to the image-receiving layer.

In the accompanying drawing:

Figs. 1 and 2 are sectional views of a film which may be used according to our process,

Figs. 3 and 4 are perspective views of two types of roll film useful according to our invention, and

Fig. 5 is a schematic view of an apparatus which may be used to process the film according to our invention.

Our invention comprises in its broader aspects a process for producing direct-positive photographic images by transfer of an image-forming compound from a lightsensitive layer to a light-insensitive layer by exposing to an object or image a light-sensitive material coated on one side of a visually opaque support, the opposite side of which support has thereon a material reactive with the transferred compound to form a visible image, treat.- ing the light-sensitive layer to form an image, rolling the support on itself so that the light-sensitive layer containing the image contacts the opposite side of the support having thereon the material reactive with the transferred compound, and maintaining contact between the lightsensitive layer and the opposite side of the support for a time sufficient to transfer image-forming compound from unexposed areas of the light-sensitive layer to the back of the support, thereby forming a visible image on the opposite side of the support. If desired, the treatment of the light-sensitive layer to form the image may be done at the point of contact between the lightsensitive layer and receiving layer.

The light-sensitive layer and the receiving or backing layer are combined in the form of a roll film or paper which may be used in ordinary roll film cameras. Between the light-sensitive layer and the receiving layer, either in the support or in aseparate layer there is a visually opaque layer to permit viewing of the transferred image. There may also be a light-impermeable layer in the element to prevent exposure during handling.

In our preferred process an exposed roll film material is removed from the camera in the normal way and transferred to a simple processing tank which can be made light-tight and which has means for drawing the exposed film through a processing bath. The exposed roll film is unrolled sufiiciently so that it can be threaded through the tank to a take-up roller. The film is then drawn through the processing solution by means of a crank on the take-up roller, under conditions such that the sensitive layer is developed or a negative image formed in it, and the sensitive layer wet with solution brought into close and firm contact with the receiving layer by winding on the take-up roller. It is also possible to use a processing apparatus having containers for two or more baths so that the film can be wound from a developing bath, for example, into a separate transfer bath or stabilizing solution.

The sensitive material need not be exposed in a camera, but may be exposed in a suitable apparatus by reflex or contact printing.

The light-sensitive layer and the light-insensitive receiving layer may be of various types depending upon the process which it is desired to employ. The light-sensitive layer may be a silver halide emulsion layer which may contain either a tanning developing agent or a nontanning developing agent or may be free of developing agent. In case a developing agent is incorporated in the emulsion a single processing bath of alkaline hypo or alkaline sulfite suffices for development of the exposed emulsion. If the emulsion is free of developing agent and is of the conventional type it maybe processed by a silver salt transfer method having the developing agent in the solution, in which case the receiving layer contains nuclei to promote physical development, for instance,-

colloidal silver, colloidal gold, silver sulfide and the like, or a precipitating agent which converts unexposed and dissolved silver salt to an insoluble form, for example, sodium sulfide or selenide, zinc sulfide, aminoguanidine sulfate, aminoguanidine carbonate, arsenous oxide, sodium stannite, thiourea or its derivatives, substituted hydrazines, organic sulfiding agents, e.g., mercaptans,

xanthates, etc. In the latter case it is desirable to have a non-wandering developing agent incorporated in the emulsion which is then processed in an alkaline solution asdescribed above. The processing solution in the case of silver salt transfer processes contains a suitable quantity of a silver salt solvent, for example, 20 grams per liter of sodium thiosulfate. It may also be desirable in this case to increase the .pH above the normal ranges of processing solutions by the addition of alkali, to add suitable .antifoggants such as benzotriazole or to employ other means, to control development rate all of which are well known in the art. Alternatively, it may be desirable to employ two-solution treatment in which case the first bath would contain a conventional black-and-white developer modified as indicated, if necessary, and the second bath would contain a suitable solution of hypo, possibly at reduced pH.

In order to produce colored images in the receiving color-forming compounds or dyes, or color-forming compounds of the type which couple with the oxidation product of primary aromatic amino developing agents may be incorporated in the developing solution.

-The light-sensitive layer may contain as the sensitizing agenta material other than a silver compound such as a diazonium salt, in which case the receiving layer would contain a diazo coupling compound and an alkali to form an image upon transfer of unused diazonium salt.

A preferred transfer process is one which depends upon the development of a negative image in a silver halide emulsion layer with subsequent solution of the undeveloped silver halide in this layer by a silver halide solvent in the processing solution, followed by transfer by diffusion of this dissolved silver halide to the receiving layer in which the silver halide is made insoluble or reduced to form a positive image. This type of process is illustrated by Examples 1 to 7 below.

Our invention will now be described by reference to the accompanying drawings wherein the preferred form of our process is illustrated.

Fig. 1 is a sectional view of a film useful according to our invention in which the support 10 consists of white pigmented cellulose acetate or cellulose acetate butyrate, or of waterproofed baryta paper with relatively smooth surfaces. This support has an opaque layer 11 which may be a heavily pigmented layer of gelatin containing a dark-colored pigment. The dark-colored pigment may also be incorporated in the support or in a substratum layer. On the opaque layer 11 there is a gelatino-silver bromoiodide emulsion layer 12 and a gelatin overcoating layer 13 to protect the negative from physical abrasion, and also to give some control of therate of diffusion of silver ions from the negative layer. The opaque layer 11 provides an anti-.halation backing for the negative and eliminates the need for a separate backing paper as in conventional roll film materials.

The receiving layer 14 in which the positive image is formed during processing is preferably a gelatin layer containing one of the nucleating or precipitating agents described above. This layer may have on its surface frame numbers which are removed during processing so that the film can be used in an ordinary roll film camera. Dyes which are rendered colorless by the alkaline nature of the developer or by the reducing action of the developing agents are satisfactory for this purpose. One such dye is bis-E1,3-diphenyl-2-thiobarbituric acid-(5)]pentamethine oxonol. In lieu of frame numbers on the film,

4' the film may be notched to provide means for stopping the film at the desired frame,

The film product as assembled for spooling is shown in Fig. 3. The film strip 9 has attached to it a leader 15 and a trailer 16 by means of pressure or heat-sensitive tapes 17 and 18. The tapes extend across the full width of the film strip and are cut flush with its edges. In addition, the tapes must be relatively water-resistant and not lose their adhesion when wet with the developing solution. The leader 15 and trailer 16 may be construct ed of ordinary roll film backing paper. It is preferable that the trailer 16 consist of relatively waterproof material while the leader 15 should be relatively water-absorbent, both having high wet strength. The free end 19 of the leader 15 is tapered to facilitate threading in the take-up spool of the camera while the free end 20 of the trailer 16 is constructed to be attached conveniently on the take-up roller of the processing box. The

1 layer, the emulsion or the receiving layer may contain leader 15 and the trai1er 16 preferably have skived edges to provide a light seal when the strip is wound on spool 21. The strip is wound on this spool so that the photo, sensitive surface 22 ultimately containing the exposed image is on the inside.

In the film shown in Fig. 2 in which like numbers indicate like parts, there is no black opaque layer between the support and the negative layer. The support 10 is a white pigmented support as in the case of Fig. l, and the emulsion layer 12, overcoating layer 13 and receiving layer 14 are the same as before. In this case a backing, paper is used as shown in Fig. 4 and the leader 15 is extended as backing paper 15a, in order to protect the filmstrip from window light while passing through the camera.

The frame numbers are placed on the backing paper;

15a rather than on the receiving layer 14. The leader 15, 15a therefore takes the form of ordinary backing paper. It is still necessary to use a trailer 16 and this;

must extend beyond the end of backing paper 15a.

A modification of the film assembly of Fig. 3 consists inthe elimination of the separate leader and trailer, using: additional lengths of the photosensitive strip to provide daylight loading of the camera and the processing box. Without the skived paper leader and trailer a special spool with indented flanges is necessary to protect the film from light fogging while in the spool.

When the position of the frame numbers is established either by numbering the back of the film strip itself as described above or by using a backing paper with numbers on it, it is possible to provide a white border around each picture. The border is provided in the form of a latent image applied by a heavily fogging exposure to all parts of the strip except within the frames where the negative images are to be placed. If this latent image is I not applied and a reversal process is used, prints with ablack border will be obtained. Alternatively a waterimpermeable resist may be printed in the border areas of either layer to prevent transfer of the unexposed silver halide in these areas.

In order to process the film constructed according to our invention an apparatus such as that shown in Fig. 5 may be employed. This apparatus consists of a lighttight box or container 23 with a hinged cover so that the film may be inserted into it on a feed spool and a take-up spool, and made to pass over a processing roller adjacent to a tank of processing solution. The film 9 from feed spool 24 is threaded over roller 25 and onto take-up roller 26, which has a crank or other means to wind the film from the feed spool to the take-up roller. The film 9 passes with emulsion side down through a trough or container 27 of processing liquid. By winding the film strip from the feed spool 24 to the take-up roller 26, successive areas of the negative side are wet with the developer or processing liquid and by winding up on the take-up roller 26, the light-sensitive side is brought contact with the receiver side of the film in order to effect the transfer. When the film strip has been wound up completely on the take-up roller and suflicient time has been allowed for the transfer to take place, the box is opened and the strip is unwound from the take-up roller. The film strip then contains a series of negative images on one side and a series of positive images on the other side, the positive images being displaced from the corresponding negative images along the length of the strip by a distance equal to the circumference of the take-up roller.

For the preferred form of our process described in Examples 1 to 6 the take-up roller should be turned at such a rate that from 4 to 8 seconds elapse between the time when a given area of film is first wet with developer at the processing roller 25 and the time at which it reaches the take-up roller 26. The film strip is allowed to remain on the take-up roller for approximately two minutes after which time the box is opened and the strip is pulled oif. The leader and trailer are cut ed and the picture frames are cut apart. Because the layers on the film are extremely thin, the reverse side of the film strip dries in about /2 minute and the negative side in about two minutes. The negative images are disregarded in cutting the positives apart.

The preparation of the nuclei for the receiving layers of Examples 1 to 6 described hereinafter is based on the use of colloid stabilizers. The nuclei are prepared by quickly mixing a dilute solution of sodium sulfide with a dilute solution of one or more metal salts, for example, zinc nitrate, lead acetate and silver nitrate in the presence of a critical amount of a colloid stabilizer. The colloid stabilizer may be present originally in either the sulfide solutionor the metal salt solution depending on the nature of the particular stabilizer. In some cases it may be necessary to adjust the acidity or alkalinity of either the sulfide solution or the metal salt solution prior to the precipitation of the colloidal metal sulfide particles in order that the stabilizer will be in a properly active state to control the size of the sulfide particles.

After a period of digestion during which the colloid stabilizer establishes the size or other characteristics of the sulfide particles, a binder such as gelatin is added which, by its own protective action on colloidal particles, will further stabilize the system. The principal reason for. adding the gelatin is to provide a vehicle for coating the sulfide particles on the support. silicates are the preferred colloid stabilizers, but materials such as aluminates, saponin, mercaptotetr'azoles and methylene blue have also been found to be useful for this purpose. To obtain the desired result, the ratio of soluble sulfide to colloid stabilizer is critical and can be varied no more than /3 to 3 times the optimum ratio. The optimum ratio, however, depends on the particular colloid stabilizer used, and varies from about 0.2 for silicates to 28 for methylene blue.

Before coating, it is desirable to add a sufiicient quantity of lead acetate to insure the production of a black tone in the transfer image. According to this method of preparing nuclei, the black tone and high density are not obtained in the absence of lead acetate; also, sulfide particles which have not been precipitated in the presence of a critical amount of the colloid stabilizer will not respond to the lead acetate to give the combination of high density and black tone.

The following examples illustrate our process. Examples 1 to 6 illustrate a solvent transfer process using a nucleatin'g agent in the receiving sheet.

Example 1 A receiving layer was made as follows:

To 120 cc. of water there was added 0.6 cc. of 0.5 M sodium sulfide and 2.5 cc. of 0.5 M sodium metasilicate at 40 C. and the solution mixed with. rapid stirring with a solution of 420 cc. of water, 0.6 cc. of 0.5 M lead acetate, 0.24 cc. of 0.5 M zinc nitrate and 0.6 cc. of 0.1 M silver nitrate, with sufficient nitric acid added to give a pH; of 3.2.. This resulted in the formation of colloidal silver sulfide, lead sulfide and possibly zinc sulfide in an excess of zinc ion. Colloidal silicic acid which acts as a peptizer is also formed and probably some zinc and lead silicates. Stirring was continued at 40 C. for two minutes, then 60 cc. of 10% gelatin solution was added, the stirring continued at 40 C. for 30 minutes and then 15 cc. of 1 N lead acetate was added. After stirring for an additional 15 minutes at 40 C., a solution of 3 cc. of 15% saponin solution and 10 cc. of 10% formaldehyde solution, with sufficient nitric acid to give a pH of 3, was added and the mixture was coated on a cellulose ester film base which had been pigmented with titanium dioxide. The coating was at the rate of 6 cc. per square foot of surface and did not need to be set by chilling.

On the opposite side of the support there was coated an: opaque layer consisting of a dispersion of carbon particles in gelatin and a gelatino-silver 'bromoiodide emulsion coated at the rate of 0.09 g. per square foot of surface. A gelatin overcoat was finally added for abrasion protection.

The film was spooled and exposed in an ordinary camera, then removed from the camera and placed in a developing apparatus similar to that shown in Fig. 5. The developer used in this apparatus had the followingv composition:

Grams Hydroquinone 32.8 Sodium sulfite (desiccated) 75 Sodium thiosulfate 14 Sodium hydroxide 26.7 Benzotriazole 0.12 Water to 1 liter.

The film was wound from the film spool to the take-up spool at such rate that 5 or 6 seconds elapsed between the time the negative first touched the developer and the time it first came in contact with the receiver surface on' the back of the sheet. After about two minutes, the film was removed from the developing cabinet and a positive image was found to be formed in the receiving layer on the back of the film.

Example 2 A receiving layer was made by first mixing rapidly at 40 C. a solution of 0.6 cc. of 0.5 M sodium sulfide in cc. of water, with a solution comprising.

0.5 M lead acetate 0.5 M zinc nitrate 0.1 M silver nitrate 15% saponin solution Water a s sahcanuscnsu6---- After two minutes, 60 cc. of a 10% gelatin solution was;

added and after stirring for 30 minutes, 15 cc. of 0.5 M lead acetate was added together with saponin and formaldehyde. The sol was coated at 6 cc. per square foot on a white TiO pigmented cellulose acetate butyrate support.

An opaque layer and a silver halide emulsion layer were coated on the opposite side of the support as in Example I and after exposure and processing as described in Example 1,. positive images were formed in the receiving layer.

Example 3 After two minutes stirring, 60 cc. of a 10% gelatin solu" tion were added and after another thirty minute stirring,-

15 cc. of 0.5M lead acetate were added. The sol was adjusted to a pH of 3 with dilute nitric acid, saponin and formaldehyde were added and the coating was made on the support of Example 2 at the same rate as in Example 2. The opposite side of the support was coated with an opaque layer and emulsion as in Example 1 and was exposed and developed as in Example 1.

Example 4 4 In the preceding examples the metal salts were present to the extent of 50% in excess of the amount required to react with the sodium sulfide. By considering the solubility of the various sulfides which may form, it is apparent that substantially all of the silver ions of the receiving layer will react to form silver sulfide and most of the lead ions will also. The most soluble sulfide is zinc sulfide, hence, zinc ions will be left in excess after the completion of the precipitation. It is possible to convert the zinc into a form which in itself will act as a colloid stabilizer. This form is the gelatinous zinc hydroxide and isproduced by adjusting the pH of the reaction mixture as shown in the present example.

A solution of 0.6, cc. of 0.5 M sodium sulfide in 120 cc. of water was mixed rapidly at 40 C. with a solution comprising Cc. 0.5 M lead acetate 0.6 0.5 M zinc nitrate 0.24 0.1M silver nitrate 0.6 Water 420 Dilute sodium hydroxide to pH 8.

After two minutes stirring, 60 cc. of gelatin solution were added and after another thirty minute stirring, cc. of 0.5 M lead acetate were added. The sol was adjusted to a pH of 3. with dilute nitric acid, saponin and formaldehyde were added and a coating was made on film base as in Example 2.

An opaque layer and emulsion were coated as described in Example 1 and the film was exposed and developed as in Example 1, and positive images were formed in the receiving layer.

- Example 5 A receiving layer was formed by mixing rapidly at 40 C. a solution of 0.6 cc. of 0.5 M sodium sulfide, 0.3 cc. of a 5% solution of 4-phenyl-5-mercaptotetrazole in 120 cc. of water with a solution comprising Cc. 0.5 M lead acetate 0.6 0.5 M zinc nitrate 0.24 0.1 M silver nitrate 0.6 Water 420 A receiving layer was formed by mixing rapidly at 40 C. a solution of 1.8 cc. of 0.5 M sodium sulfide and 6 cc. of 0.5 M sodium metasilicate in 120 cc. of water with a solution comprising Cc. 0.5 M lead acetate 1.8 0.5 Mzinc nitrate 0.72 0.1 M silver nitrate 1.8 Water 390 Dilute nitric acid to pH 3.2.

After two minutes stirring, cc. of a 20% gelatin solution were added and after another thirty minute stirring, 8.4 grams of lead acetate were added. After a further fifteen minute stirring, the pH was adjusted to 3 with dilute nitric acid, saponin and formaldehyde were added, and the sol was coated at 2 cc. per square foot on the support of Example 2.

An opaque layer and an emulsion layer were coated as in Example 1 and the film was exposed and developed as described in Example 1 to form positive images in the receiving layer.

Example 7 This example describes a solvent transfer process using a precipitating agent which precipitates stoichiometric amounts of silver from the transfer image.

An emulsion was made by preparing solutions of (A) 25 grams of gelatin in one liter of water at 40 C., (B) grams of silver nitrate in 500 cc. of water at 20 C. and (C) 35 grams of sodium chloride in 500 cc. of water. Solutions (B) and (C) were simultaneously run into solution (A) at a uniform rate while stirring the latter over a period of about 10 minutes; solution (-B) preferably was not allowed to run in faster than solution (C). Thereafter 150 grams of gelatin in 1500 cc. of water at 40 C. were added. The pH of the emulsion was then adjusted to 5 and a developing agent consisting of 25 grams of 3,4-dihydroxydiphenyl dissolved in 250 cc. of methyl alcohol was added. This solution was added slowly to the emulsion with stirring and the developing agent became dispersed in the emulsion in minute crystals. Thirty cc. of 10% formaldehyde solution were thenadded and the composition coated on a pigmented film base as in Example 1.

The opposite side of the film base was coated with a gelatin solution containing 4% of ammonia and 3% of amin-oguanidine sulfate.

The emulsion was exposed to a line image and developed in a 3% sodium carbonate solution for about 15 seconds. Excess alkaline solution was removed from the emulsion surface by squeegee and the emulsion layer was then rolled into contact with the receiving layer. After 5 or 10 seconds contact, the film was unrolled and a positive image was found to be formed in the receiving layer.

Example 8 This example illustrates the transfer of a coupler from the emulsion layer to a receiving layer containing an oxidized color developing agent.

A fine-grain silver chloride dispersion was prepared by adding simultaneously and at a moderate rate a mixed solution of 70 cc. of l N potassium chloride solution and 25 cc. of 0.2 N potassium bromide solution diluted to a volume of cc., and 80 cc. of 1 N silver nitrate solution also diluted to a volume of 125 cc., to a well agitated solution of 250 grams of 10% de-ashed gelatin solution and 500 cc. of water. The total weight of the silver chloride dispersion was 1000 grams.

A mixture of 5.35 grams of 5-chloro-2-hydroxy-4- methyl thioglycolic anilide, 40 cc. of ethyl alcohol and 4.4 cc. of a 20% aqueous sodium hydroxide solution was heated to ll0120 F. for 5 to 8 minutes. To the clear solution there was added 35 cc. of water and the whole added slowly with good stirring to 400 grams of the silver chloride dispersion described above. A dispersion of the silver salt of a cyan coupler was thus obtained.

To 112 grams of a gelatino-silver bromoiodide emulsi-on there was added 194 grams of the coupler dispersion together with suitable quantities of hardening agent, antifoggant and saponin spreading agent. The coupler-containing emulsion was then coated on a film base which had previously been coated with a receiving layer as described below.

Prior to coating the coupler-containing emulsion, the film base had been coated with a gelatin solution contain- Z-amino-S-diethylarninotoluene sulfate and then treated with a 2% solution of potassium ferricyanide to form the oxidation product of the color developing agent.

After exposure of the coated emulsion, the film was given a two-bath treatment. It was developed for minutes in the following color developer:

Benzyl alcohol cc 15 Trisodium phosphate grams 100 Potassium bromide do 2.5 Sodium sulfite do 1.5 d-Iso-ascorbic acid do 0.25 Z-amino-S-diethylaminotoluene sulfate do 4 Water to 1 liter.

Film was then passed through a fixing bath containing a silver halide solvent such as acid hypo, of the following composition:

Sodium thiosulfate grams 240 Sodium sulfite do Sodium bisulfite do 25 Water to 1 liter.

The fixing bath removes the undeveloped silver halide from the film and also removes silver from the unused coupler, rendering it diffusible in the presence of alkali. The surface of the film was then moistened with alkali and rolled into contact with the receiving layer containing the developer oxidation product. Diffused coupler reacted with the oxidized developer, forming a positive image in the transfer layer.

Example 9 This example illustrates the transfer of a developer component from the sensitive layer to a receiving layer containing a color coupler.

On a cellulose ester support there was coated a solution of the following composition:

Gelatin, 10% solution cc 100 Water cc- 50 Formaldehyde, 10% solution cc 2 4-amino-N-ethyl-N-(B methane-sulfonamidoethyl)- m-toluidine grams 2 Gelatin, 10% solution cc 228 Alkanol B, 5% solution cc 27 Water cc 95 The opposite side of the support was coated with a gelatin layer containing a color coupler made by adding 50 cc. of the above coupler dispersion to 150 cc. of 10% gelatin solution and 2 cc. of 10% formaldehyde solution. Potassium periodate was then added and the solution stirred until saturated. Excess potassium periodate was allowed to settle and the clear solution was coated on the support and dried.

The emulsion was exposed to an image and the film was treated for 10 seconds in a 5% sodium carbonate solution. This causes the developing agent to diffuse and reduce the exposed silver halide to metallic silver. The oxidation product of the developer reacting with the color coupler in the sensitive emulsion forms a non-diffusing dye. After treatment in the alkaline solution excess was removed from the element by squeegee and the film was then rolled into intimate contact with the alkali moistened surface of the film for 30 seconds. Diffusion takes place between the two sides of the fi m. and unused developing agent available only where partial exposure or no exposure of the silver halide existed, diffused to the receiving sheet where it was oxidized by the oxidizing agent. The oxidized developer then reacted with the coupler in the receiving sheet toform a positive image. When the two layers were separated, the receiving surface exhibited a positive image.

Transfer of an image may also be effected by a dye imbibition process, instead of by a color developer transfer process as in this example.

Example 10 This example illustrates the transfer of a diazo component to a diazo coupler in the receiving layer.

Waterproofed paper was coated with a baryta-gelatin mixture and allowed to dry. After drying, this layer was impregnated with a solution of 20 parts of the diazo compound obtained from diethylamino-m-toluidine hydrochloride, 5 parts of tartaric acid and parts of water and dried. The opposite side of the support which was to act as the receiving surface was coated with a baryta-gelatin mixture, dried and impregnated with a solution of 2 parts of phloroglucinol, 5 parts of anhydrous sodium carbonate and 100 parts of water and dried.

The sensitive side of the sheet was exposed to a line positive image at a distance of 18 inches from a mercury vapor arc for 5 to 10 seconds and was then rolled into contact with the moistened surface of the receiving layer. After the exposed layer and the receptor layer had been in contact for several seconds, they were separated and an azo dye positive image was found in the receptor layer. If desired, the sodium carbonate in the receptor layer can be omitted and the layer fumed with aqueous ammonia after contact or an alkaline solution applied to it instead of wetting the receptor layer with water prior to contact.

The examples herein are illustrative only and it is to be understood that our invention is to be taken as limited only by the scope of the appended claims.

We claim:

1. A process for producing direct positive photographic images by transfer of a silver compound from a lightsensitive layer to a light-insensitive layer which comprises exposing to an object or image a photographic silver halide emulsion layer coated on one side of an opaque support, the opposite side of said support having thereon a backing layer containing silver salt physical development nuclei, treating said emulsion layer with an alkaline solution in the presence of a silver halide developing agent to initiate and promote development of the silver halide, rolling the support on itself so that the developed and wet emulsion layer contacts the backing layer containing the physical development nuclei, in the presence of a silver halide solvent, and maintaining contact between the emulsion layer and the backing layer for a time sufficient to transfer silver salt from the undeveloped areas of the emulsion layer to the backing layer, thereby forming a positive image in the backing layer.

2. A process for producing direct positive photographic images by transfer of a silver compound from a lightsensitive layer to a light-insensitive layer, which comprises exposing to an object or image a photographic silver halide emulsion layer coated on one side of an opaque support, the opposite side of said support having thereon a backing layer containing a silver precipitating agent, treating said emulsion layer with an alkaline solution in the presence of a silver halide developing agent to initiate and promote development of the silver halide, rolling the support on itself so that the developed and wet emulsion layer contacts the backing layer containing the precipitating agent, in the presence of a silver halide solvent, and maintaining contact between the emulsion layer and the backing layer for a time sutfi- 11 cient to transfer silver salt from the undeveloped areas of the emulsion layer to the backing layer, thereby precipitating a positive image in the backing layer.

3. A process for producing direct positive photographic images by transfer of a silver compound from a light-sensitive layer to a light-insensitive layer, which comprises exposing to an object or image a photographic emulsion layer of hardened colloid containing silver halide and a silver halide developing agent which is substantially non-diffusing in said colloid, which layer is coated on one side of an opaque support, the opposite side of said support having thereon a light-insensitive receiving layer, rolling the support on itself and contacting the light-sensitive layer with the receiving layer in the presence of an alkaline solution, a silver halide solvent and a silver precipitating agent, to form a positive image in said receiving layer.

4. A process for producing direct positive photographic images by transfer of a silver compound from a light-sensitive silver halide emulsion layer to a light-insensitive layer, which comprises exposing to an object or image a photographic emulsion layer of hardened colloid containing silver halide and 3,4-dihydroxy diphenyl as a silver halide developing agent which is substantially non-difiusing in said colloid, which layer is coated on one sde of an opaque support, the opposite side of said support having thereon a light-insensitive receiving layer having a coating of an ammonium compound and aminoguanidine sulfate at least on its surface, rolling the support on itself and contacting the light-sensitive silver halide emulsion layer with the receiving layer in the presence of a sodium carbonate solution, to form a positive image in said receiving layer.

5. A process for producing direct-positive photographic images by transfer of a silver compound from a light-sensitive layer to a light-insensitive layer, which comprises exposing to an object or image a silver halide emulsion coated on one side of an opaque support, the opposite side of said support having thereon a backing layer containing as nuclei for transferred silver compound, metal sulfide particles having a colloid stabilizer adsorbed thereto, treating said light-sensitive layer to form an image therein, rolling the support on itself so that the light-sensitive layer containing the image contacts the backing layer containing the metal sulfide particles and maintaining contact between the light-sensitive layer and the backing layer for a time sufficient to transfer a soluble silver compound from unexposed areas of the light-sensitive layer to the backing layer, thereby forming a visible image in said backing layer.

6. The process of claim 5 in which the metal sulfide is zinc sulfide.

7. The process of claim 5 in which the metal sulfide is lead sulfide.

8. The process of claim 5 in which the metal sulfide is a mixture of zinc sulfide and lead sulfide, and the colloid stabilizer is a colloidal silicate.

References Cited in the file of this patent UNITED STATES PATENTS 1,444,217 Sparks Feb. 6, 1923 2,052,621 Gurwick Sept. 1, 1926 2,171,911 Bloch Sept. 5, 1939 2,352,014 Bott June 20, 1944 2,563,342 Land Aug. 7, 1951 2,635,048 Land Apr. 14, 1953 2,699,393 Weyde Jan. 11, 1955 

1. A PROCESS FOR PRODUCING DIRECT POSITIVE PHOTOGRAPHIC IMAGES BY TRANSFER OF A SILVER COMPOUND FROM A LIGHTSENSITIVE LAYER TO A LIGHT-INSENSITIVE LAYER WHICH COMPRISES EXPOSING TO AN OBJECT OR IMAGE A PHOTOGRAPHIC SILVER HALIDE EMULSION LAYER COATED ON ONE SIDE OF AN OPAQUE SUPPORT, THE OPPOSITE SIDE OF SAID SUPPORT HAVING THEREON A BACKING LAYER CONTAINING SILVER SALT PHYSICAL DEVELOPMENT NUCLEI, TREATING SAID EMULSION LAYER WITH AN ALKALINE SOLUTION IN THE PRESENCE OF A SILVER HALIDE DEVELOPING AGENT TO INITIATE AND PROMOTE DEVELOPMENT OF THE SILVER HALIDE, ROLLING THE SUPPORT ON ITSELF SO THAT THE DEVELOPED AND WET EMULSION LAYER CONTACTS THE BACKING LAYER CONTAINING THE PHYSICAL DEVELOPMENT NUCLEI, IN THE PRESENCE OF A SILVER HALIDE SOLVENT, AND MAINTAINING CONTACT BETWEEN THE EMULSION LAYER AND THE BACKING LAYER FOR A TIME SUFFICIENT TO TRANSFER SILVER SALT FROM THE UNDEVELOPED AREAS OF THE EMULSION LAYER TO THE BACKING LAYER, THEREBY FORMING A POSITIVE IMAGE IN THE BACKING LAYER. 